Prior art workers have devised many types of powered, hand-held, fastener driving tools. The tools can be designed to drive various types of fasteners such as nails, staples, blind rivets, and the like. The fastener driving tools may be driven by compressed air, internal combustion means, or electrical means such as a solenoid, or a flywheel assembly. The present invention is applicable to such fastener driving tools, and is not specifically limited to the types of fasteners being driven or the drive means of the tool. For purposes of an exemplary showing, the invention will be described in terms of its application to a pneumatic fastener driving tool designed to drive nails.
The invention is applicable to any situation wherein a first workpiece is to be attached to a second workpiece, the first workpiece having a pre-existing hole through which the nail is to be driven into the second workpiece, to join the workpieces together. Fastener driving tools in general, and nailers in particular, are fairly large, bulky tools comprising a main body portion, a handle portion, a magazine portion and a guide body. The guide body contains the drive track for the nails, the forwardmost nail in the magazine being driven out of the drive track by a piston powered driver. The lowermost part of the guide body, generally referred to as the tool nose portion, is such that it would be substantially impossible to accurately line up the drive track of the tool with a pre-existing hole in a workpiece having a diameter to just nicely receive the shank of a nail.
One of the most common instances where this problem arises is found in the attachment of metallic brackets to wooden structural frame members to join the structural frame members together in a fixed relationship with respect to each other. The brackets are normally formed of sheet metal or plate. If the drive track of a nailer is not properly aligned with a pre-formed nail hole in the metallic bracket, the bracket will not be properly attached to the wooden workpiece and it could also further result in deformation of the forwardmost nail, which might become jammed in the drive track.
Prior art workers have attempted to solve this problem in a number of ways. U.S. Pat. No. 4,928,867 teaches the use of metallic brackets or connectors which have particular formations formed therein in conjunction with each hole. These may constitute inner and outer raised tings on the metallic connector surrounding a nail hole and forming a groove there between, an arcuate raised ridge, a series of tabs, or the like. The fastener driving tool an alignment foot which coacts with these formations to align the drive track with the nail hole in the connector or bracket.
U.S. Pat. No. 5,193,730 teaches a pneumatic nailer provided with a nail push piston mechanism which separates the forwardmost nail from the strip thereof and extends the forwardmost nail below the nailers' nose portion. A nail holding mechanism firmly engages the body portion of the nail, maintaining the nail in its protruding position so that it can be used to find a hole. Once so positioned, the nail is driven in place, the holding mechanism releasing the nail.
U.S. Pat. No. 5,238,167 teaches a nailer having a probe by which proper alignment of the drive track and a pre-existing hole is achieved. The probe is moved out of the way by the nail during the driving thereof.
The present invention is based upon a different approach. An otherwise standard pneumatic nailer is provided with a modified guide body and a modified magazine. The magazine is made up of an inner magazine portion which carries a strip of nails. The inner magazine portion is surrounded by an outer magazine portion attached to the handle portion of the pneumatic nailer and the guide body. The inner magazine portion is pivoted at its rearward end within the outer magazine portion and is shiftable between a first position wherein the forwardmost nail of a strip is extended beyond the nose sufficiently to enable the forwardmost nail to act as a probe and to locate and enter the preformed nail hole through which it is to be driven, and a second position wherein the forwardmost nail of the strip remains in the hole and is positioned to be driven. Once the hole is located, the tool is pressed toward the workpiece causing the inner magazine portion to achieve its second position. The inner magazine portion is operatively connected to a safety trip which, when the inner magazine portion is shifted from its first position to its second position, shifts with it from a first trigger disabling position to a second trigger enabling position, so that the nail may be driven by the nailer. The inner magazine portion and the trip are biased to their first positions. This is basically a simpler and less complicated approach which requires no special probe, no special means to separate the forwardmost nail from the nail strip, and no special configurations on the first workpiece which has the preformed hole.